Finding the Fourth Proportional to 5,405.91, 8,111.39 and 5,318.55

Step by Step Solution

1. Step 1: Write the proportion equation
   5,405.91 : 8,111.39 = 5,318.55 : x
2. Step 2: Convert to fraction form
   5,405.91/8,111.39 = 5,318.55/x
3. Step 3: Cross multiply
   5,405.91x = 8,111.39 × 5,318.55
4. Step 4: Simplify right side
   5,405.91x = 43,140,806.69
5. Step 5: Solve for x
   x = 43,140,806.69/5,405.91
6. Step 6: Final answer
   x = 7,980.30